—Math is too difficult, I nearly give it up.

—Please don't, nothing is ______ if you put your heart into it. [ ]

A. important

B. impossible

C. interesting

可以抗肿瘤、抗衰老、抗感染、降血糖血脂的化合物是（）。

A.谷维素

B.植物多酚

C.活性多糖

D.磷脂